1. Field of the Invention
This invention relates generally to electrophotographic copying machines, and, in particular, to a compact, table top plain paper copy machine that consumes a minimal amount of energy.
2. Description of the Prior Art
Plain paper electrophotocopying machines are well-known devices that reproduce images of original documents on ordinary or plain paper. Such machines typically include a reusable photoreceptor including a conductive substrate coated with a photoconductive material, a supply of plain paper copy sheets, and a plurality of processing stations for operating on the photoconductor and the copy sheets. In a typical sequential copying process, the photoconductor is uniformly charged and then exposed to an illuminated, original document. The areas of the photoreceptor that are struck by the image of the indicia carried on the original retain their charge and the charge in the light-struck areas is dissipated. Thus, a latent electrostatic image is formed on the photoconductive coating of the photoreceptor. Next, the latent image is developed by contacting the photoreceptor with electrically attractable toner particles which adhere to the charged areas of the photoconductive coating that make up the latent image. The toned image is next transferred to the copy sheet where the toner is fused onto the sheet to fix the image thereon.
Early models of plain paper copiers were, in general, large, expensive and complex machines that constantly consumed energy, even in an idle or stand-by mode. Such machines were large in size since they used either a relatively large radius drum for supporting a photoreceptor or used a belt or web type photoreceptor that moved through an elongated path past the copy processing stations. Unfortunately, such machines are not practical for some users who have a limited amount of office space or modest copying requirements.
Accordingly, others have attempted to reduce the size of plain paper copiers ad otherwise simplify their operation in order to meet the spatial and economic requirements of the relatively low volume user who desires plain paper copies. See, for example, U.S. Pat. Nos. 4,012,138, 4,017,170, 3,819,261 and 3,606,532 as illustrative of such attempts. However, the devices as described in the above patents suffer from one or more drawbacks including the use of a drum supported photoreceptor which occupies a relatively large volume of space, a moving optical system which can be expensive and complex in operation, separate toning and cleaning stations, and a fuser that constantly requires energy even when copies are not being made. Such attempts at size reduction often result in devices that are difficult to service since access to key operating components in need of service may be obscured by other closely spaced components. Accordingly, there is a need for a compact machine with closely spaced and readily accessible operating components.
A number of copy machines employ a belt or web type of photoreceptor. Such photoreceptors will naturally track to one side of the pulley or roller that supports the belt, thus misaligning the photoreceptor. Others have solved this problem by using crowned drive and support rollers. But such solutions are expensive so there remains an unfilled need for a relatively simple and inexpensive belt alignment system.